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HISTOGAUSS

HISTOGAUSS

Name


      HISTOGAUSS

Purpose


      Histograms data and overlays it with a Gaussian. Draws the mean, sigma,
      and number of points on the plot.

Calling Sequence


      HISTOGAUSS, Sample, A, [XX, YY, GX, GY, /NOPLOT, /NOFIT, FONT=,
                              CHARSIZE = ]

Input


      SAMPLE = Vector to be histogrammed

Output Arguments


      A = coefficients of the Gaussian fit: Height, mean, sigma
              A[0]= the height of the Gaussian
              A[1]= the mean
              A[2]= the standard deviation
              A[3]= the half-width of the 95% conf. interval of the standard
                    mean
              A[4]= 1/(N-1)*total( (y-mean)/sigma)^2 ) = a measure of
                      normality
      Below: superceded. The formula is not entirely reliable.
      A[4]= measure of the normality of the distribution. =1.0, perfectly
      normal. If no more than a few hundred points are input, there are
      formulae for the 90 and 95% confidence intervals of this quantity:
      M=ALOG10(N-1) ; N = number of points
      T90=ABS(.6376-1.1535*M+.1266*M^2) ; = 90% confidence interval
      IF N LT 50 THEN T95=ABS(-1.9065-2.5465*M+.5652*M^2) $
                  ELSE T95=ABS( 0.7824-1.1021*M+.1021*M^2) ;95% conf.
      (From Martinez, J. and Iglewicz, I., 1981, Biometrika, 68, 331-333.)
      XX = the X coordinates of the histogram bins (CENTER)
      YY = the Y coordinates of the histogram bins
      GX = the X coordinates of the Gaussian fit
      GY = the Y coordinates of the Gaussian fit

Optional Input Keywords


      /NOPLOT - If set, nothing is drawn
      /FITIT If set, a Gaussian is actually fitted to the distribution.
              By default, a Gaussian with the same mean and sigma is drawn;
              the height is the only free parameter.
      CHARSIZE Size of the characters in the annotation. Default = 0.82.
      FONT - scalar font graphics keyword (-1,0 or 1) for text
      /WINDOW - set to plot to a resizeable graphics window
      _EXTRA - Any value keywords to the cgPLOT command (e.g. XTITLE) may also
              be passed to HISTOGAUSS

Subroutine Calls


      BIWEIGHT_MEAN, which determines the mean and std. dev.
      AUTOHIST, which draws the histogram
      GAUSSFIT() (IDL Library) which does just that

Revision History


      Written, H. Freudenreich, STX, 12/89
      More quantities returned in A, 2/94, HF
      Added NOPLOT keyword and print if Gaussian, 3/94
      Stopped printing confidence limits on normality 3/31/94 HF
      Added CHARSIZE keyword, changed annotation format, 8/94 HF
      Simplified calculation of Gaussian height, 5/95 HF
      Convert to V5.0, use T_CVF instead of STUDENT_T, GAUSSFIT instead of
          FITAGAUSS W. Landsman April 2002
      Correct call to T_CVF for calculation of A[3], 95% confidence interval
                P. Broos/W. Landsman July 2003
      Allow FONT keyword to be passed. T. Robishaw Apr. 2006
      Use Coyote Graphics for plotting W.L. Mar 2011
      Better formatting of text output W.L. May 2012



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